1. Field of the Invention
The present invention generally relates to microwave circuit technology. In particular, some example embodiments relate to trapping or filtering out electromagnetic interference (EMI) using microwave circuits.
2. Related Technology
Electronic devices and components operating at high frequencies typically produce and emit electromagnetic fields that cause electromagnetic interference. This electromagnetic interference, referred to as “EMI,” is undesired electrical noise resulting from the electromagnetic fields. The phenomenon is undesirable because EMI can interfere with the proper operation of other electrical components.
Optical transmitter or transceiver packages, especially those operating at high transmission speeds, typically include several such electronic devices and components and are therefore especially susceptible to emitting EMI. In particular, the physical configuration of existing transmitter modules does a poor job of containing EMI—especially as the generating speed of the module increases. For example, optical transmitters often emit unacceptable levels of EMI at frequencies that are a multiple of the transmission bit rate (e.g., 10 Gbps, 20 Gbps, or 30 Gbps).
Mechanical means, such as an EMI cage, can be useful in limiting some of the EMI emissions from electronic packages. For example, an EMI cage can be sized to fit about the exterior portion of a transmitter module and configured to intercept EMI that is emitted from electronic components contained within the transmitter module. Such cages, while effective at reducing EMI, are nonetheless accompanied by certain disadvantages. Among these is the additional design complexity of the transmitter operating environment that results from the use of such cages, as well as the additional space required for the cages in the operating environment. Additionally, the cage is adjacent the exterior of the transmitter module, which places it further away from the EMI sources that are located within the transmitter module. As EMI commonly follows a diverging path as it radiates away from its source, this requires relatively more cage material to be used to prevent EMI emission than if the EMI were attenuated closer to the EMI source.
Furthermore, an EMI cage typically has one or more entry points for inputs and/or outputs through which EMI may escape. An EMI gasket and/or EMI paste can be used to reduce such emissions, but some EMI will often escape through the entry point(s), particularly due to components that may be located near the entry point(s). The EMI cage will also do little to prevent EMI from affecting other components within the cage.
The subject matter claimed herein is not limited to embodiments that solve any disadvantages or that operate only in environments such as those described above. Rather, this background is only provided to illustrate one exemplary technology area where some embodiments described herein may be practiced.